This invention relates to an apparatus for measuring the hardness of materials by measuring the difference in penetration of a penetrator under minor and major loads, for example in testing devices for Rockwell tests.
Hardness testing devices have been widely sold for many years. These devices are utilized to determine the hardness of a material, and one conventional procedure for determining such hardness is to determine the difference in penetration of a tip under minor and major loads. These test procedures have been largely performed by skilled personnel over many years, and the sensitivity or experience of the operator largely contributes to the quality and value of the test results.
Unfortunately, such human factors which materially affect the conducting of such hardness tests are undesirable, because of the differences between operators and the increasing difficulty to develop and find personnel who are qualified and trained to perform such tests.
Digital readers for displaying the results hardness tests have been widely employed in such testers, but relatively foolproof and fail-safe measurement techniques are not generally available.
Hardness tests are conducted which relate to a variety of standard scales. Although a measurement can be made and a display produced in one scale, it may be necessary for the operator to be able to quickly determine the reading in another scale. This is generally done by the operator consulting various tables and converting the reading in one scale to that in another scale. Such human conversion often is fraught with errors, and the ability to reliably convert the reading from one scale to another is not readily available and can be time consuming.
Sometimes as the minor load is applied by raising the elevating screw to have the workpiece contact the penetrator, the motion of the elevating screw is reversed. This reversal of direction as the minor load is being applied causes inaccuracies to develop in the measurement process. It is desirable that measurements not be made when there has been such direction reversal to prevent an invalid measurement to be made. In the past, such reversals of the elevating screw would only be known by the operator, and there would be no way for anyone else to know whether or not the test was properly conducted.
As the minor load is applied, sometimes the elevating screw moves too far causing an overload or overset for the minor load. Here again, due to the human element in the measurement procedures, such overset will only be known by the operator, and the measurement can proceed producing invalid data.
It is important to standardize the measuring procedures from machine to machine. One of the most critical aspects of the test procedure is the rate of application of the major load to the workpiece. Such rate control is not controlled from machine to machine, and this factor contributes to a lack of standardization between machines. This can lead to inaccuracy and unreliability in the hardness measurements, and it is an undesirable aspect of hardness testers.
The hardness measuring procedures described above are generally manually controlled. The time at which the major or minor loads are to be applied and/or removed is generally dependent upon the operator's ability and experience. An important aspect of determining the hardness of the material being tested is to properly apply and remove the major and minor loads at the proper times in the procedures, so that an inaccurate measure of the hardness of the material under test is prevented.
Hardness tests are performed according to certain ASTM standards. These standards relate to the type of materials being tested. Additionally, certain ASTM standards apply to metals, plastics and other types of materials, and in order to determine the proper standards, the operator must consult various tables prior to the test procedure. Clearly, the likelihood of human error is always present, and improper ASTM standards can be applied during the test procedure resulting in inaccurate and unreliable measurements which may not be detected because one may not be able to know that the operator used incorrect standards.
Another aspect of the prior art hardness testers relates to the choices of the major load, minor load and penetrator tip. The load to be applied as well as the penetrator tip relates to the scale and the type of test being employed. For a superficial test, lower major and minor loads are used, but this may not be followed when the measurement is run because manual selection of the proper load and tip is required.
The shape of the material being tested is an important factor in its hardness reading. If the material being tested is cylindrical, there are certain correction factors, such as the inside and outside diameters of the workpiece, and these factors must be considered in the test results. Here again, the operator must consult separate tables, and hopefully, if the operator correctly finds the proper point and the proper tables and then makes the proper corrections, an accurate measurement will be provided. Unfortunately, often there are human errors in this process, and the correction for the cylindrical shape of the device is not properly made.
Certain parts are regularly tested for hardness. Each time the part is to be tested, the operator determines the appropriate test procedures, the proper loads and the proper standards. Here again, the operator's subjectivity could lead to incorrect measurements of the material being tested.
Certain operators may find difficulty in consulting and working with various printed tables and in following specific instructions. The ability to provide a multi-sensory set of instructions, standards and procedures to the operator can materially enhance the validity and reliability of the test procedures.
Although certain prior hardness testers provide digital readouts, there is, as yet, no reliable prior art devices in which information and data are stored to be used during test operations. For product reliability standards as well as historical data, such a facility would be desirable, and this is unavailable in the prior art.
An object of this invention is to provide an improved tester for measuring the hardness of the materials.
Still another object of this invention is to provide such a tester in which the human error encountered in prior art devices is substantially eliminated.
Another object of this invention is to provide the operator the ability to automatically convert from one test scale to another test scale and reliably display the test in any desired scale.
Yet another object of this invention is to insure that the test procedure is performed properly and inhibit the test if there is an overset in the application of the minor load or a reversal of the movement of the elevating screw.
Another object of this invention is to provide a multi-sensory facility to provide both voice and visual information including standards and operating procedures so that the operator more reliably will follow the proper tests according to direction.
Another object of this invention is to effectively determine the exact time at which the major load is to be applied and to be removed, and to determine the proper time at which the hardness measurement is to be made.
Still another object of this invention is to provide such a tester in which the ability to automatically correct for material variations and shape is effectively and automatically incorporated within the apparatus, such that the operator need merely insert data to automatically correct for that inserted data.
Another object of this invention is to provide a tester in which for certain parts which are recurrently tested, the machine will automatically detect and sense the proper operating test procedures and conditions to minimize human error.
Yet another object of this invention is to provide an apparatus in which the proper minor and major loads as well as the penetrator type is displayed to the operator according to the scale in which the test is to be made.
Another object of this invention is to insure that the tester operates within proper standards, and this is accomplished by utilizing standard test blocks and running the tests to compare the results with standard ASTM standards for those blocks for such reliability checks.
Yet another object of this invention is to provide a data storage and display apparatus in which the statistical data relating to the tests can be effectively stored, retrieved and utilized for various aspects in the testing operations.
Yet another object of this invention is to provide such a test apparatus in which the ability to convert to a measurement in one scale from another and display the same is readily accomplished by automatically displaying and scrolling to the desired scale according to information entered into the machine.
Other objects, advantages and features of this invention will become more apparent from the following description.